Apparatus for producing electrically welded pipe and tubing



Aug, 1, 1933. w. SYKES 1,920,900

APPARATUS FQR PRODUCING ELECTRICALLY WELDED PiPE AND Tl lB ING OriginalFiled Jan. 9, 1928 2 She ets-Sheet 1 351 15 clam/ Aug. 1, 1933. w. sYK1,920,900

APPARATUS FOR PRODUCING ELECTRICALLY WELDED PIPE AND TUBING I OriginalFiled Jan. 9,,l928 I 2 Sheets-Sheet 2 $513 emi s flbtommx, I

Patented Aug. 1, 1933 UNITED STATES APPARATUS FOR PRODUCING ELECTRI-CALLY WELDED PIPE AND TUBING Wilfred Sykes, Chicago, 111., assignor, bymesne assignments, to Clayton Mark & Company, Chicago, Ill., aCorporation of Delaware Original application January 9, 1928, Serial No.245,309. Divided and this application June 5, 1930. Serial No. 453,302

Claims.

My invention relates to electrically welding pipes or tubing. Buttwelding thin walled tubing by an alternating current of 10,000 amperesor above applied by water cooled copper rolls 5 adjacent to the weldingseam has been extensively used, but in such an operation the periodicvariation of the alternating current causes the weld to be more perfectat the points of maximum flow of the current and less perfect at thepoints corresponding to the zero flow. This action results in astitch-like and interrupted weld which renders the tubing unfit towithstand internal pressures. I am enabled to overcome these defects andproduce a continuous weld by use of direct current supplied by aspecially controlled low voltage generator. My invention also comprisesvarious features which I shall hereinafter describe and claim. Thepresent application is a division of my application Serial No. 245,309,'filed January 9, 1928.

In the accompanying drawings, Fig. 1 is a diagrammatic view of apparatusand electrical circuits which may be employed in carrying out myinvention; Fig. 2 is a plan showing the assembly of the welding rollswith feed rolls and other instrumentalities; Fig. 3 is an elevationthereof; Fig. 4 is a detail of the edging and guiding mechanism; Fig. 5is a section of the welding and guide rolls and the mountings therefor;and Fig. 6 is an enlarged 'detailed section of the welding andguiderolls.

Referringmore specifically to the drawings, the direct current forwelding is supplied by a separately excited generator 2, which is driven35 by any suitable motor 3, here indicated as a direct curr'ent machine.Also driven by the motor 3 is an exciter 4 connected in the circuit 5with the field 6 of the generator 2 and the adjusting rheostat Go forthat field, the operation of which is controlled by a relay 7 whichinserts and cuts out a resistance 8 so that the excitation of thewelding generator may vary between predetermined maximum and minimumvalues. The operation of the relay 7 is controlled by the direct currentflowing from the generator 2 to the welding rol1s9 through the maincircuit conductors '10, and may be adjusted by any known means so as tomake it operate when the current in the welding circuit reaches apredetermined value.

When the resistance 8 is cut into the exciter circuit 5 under steadyconditions the current flowing through the welding rolls 9 is less thanthe desired value, andwhen the resistance is out out, the currentflowing through the welding rolls is higher than the desired value.Hence, when the relay '7 is properly adjusted it will cut in andshort-circuit the resistance 8 at such intervals as would maintainsubstantially the desired current flow to the welding rolls 9.. As 0 thecurrent in the armature of'the welding generator 2 does not immediatelyfollow the changes in the exciting current because of the magneticinertia of the generator field, it is possible with such a relay tomaintain a current in the armao5 ture circuit which varies but slightlyfrom a constant value. I

The frequency at which the resistance 8' is cut in and out of theexciting circuit 5 will vary with the voltage required across thewelding rolls 9 to maintain the current desired. If a high voltage isrequired, the resistance will be cut out of the exciter circuit agreaterproportion of the time than if a lower voltage is required.

The resistance 8 is also adjustable so as to permit the desired amountof resistance to be out out dependent on the voltage which it is desiredto use. The voltage may normally be varied from 3 to 6 volts, dependingon the wall thickness of the stock to be welded.

The welding unit, best shown in Figs. 5 and 6, comprises the rolls 9 anda supporting or guide roll 11. The two welding rolls are shown in theform of water cooled hopper rolls, preierably inclined at an angle of 45degrees to the verticalaxis of the machine passing through the tubes tobe welded, so that the pressure of the rolls 9 is applied across theseam and also vertically on the guide roll 11' underneath the tube tohold it firmly and prevent distortion; The guide roll 11 has insulatedbearings 13, and these bearings may be adjusted by springs 14, thecompression of which is controlled by bolts 15 to per- 'mit the guideroll to adjust itself to variations in pressure and differences in sizesof pipe and to compensate for wear, etc.

The shafts 16 of the welding rolls 9 are mounted in insulated. bearings1'? from the frame 18 of the machine, and each roll is driven throughthe gears 19 and 20, one of which (in this instance the gear 19) isformed of Micarta or other similar insulating material so that there maybe no leakage of current through the gears to the other members of themachine. The shaft 16 of each welding roll 9 is hollow so as to providefor a supply of a cooling medium such as water, which passes from theconnection 21 through the pipe 22, the lower end of which is carried inthe stationary sleeve bearing 23, to the cooling chamber 24 in the roll9, and the overflow passes out through a channel 25 between the pipe 22and the inner wall of the shaft 16 and is caught in a drain trough 26,as indicated.

The current is conducted to the weldingrolls 9 from the conductors 10through a stationary brush ring 27, on which the brushes 28 are mounted,to a collector ring 29 secured on the welding roll shaft.

In welding tubes by the instrumentalities just described, the blank orunfinished pipe A, which has previously been formed into tube shape withan open seam a, is advanced by the driven rolls 30 in such manner that afixed scraper or rasp 31 will project down into the seam a and clean andabrade its edges. The rasp 31 is so positioned that it will at the sametime bring the seam a into alignment with the path across which thewelding current is intended to pass between the rolls 9.

The blank A is then driven forward into the pass between the rolls 9 and11 by the horizontally disposed rolls 32, which brings the edges of theseam or together and trues the tube into circular form. As the weldingrolls 9 are arranged at an angle of approximately 45 degrees to thevertical axis of the tube, pressure is applied notonly to force theedges of the seam firmly against each other, but also to hold the tubefirmly in the grooved guide roll 11 underneath. While this welding rollpressure is not such as to cause any upsetting of the edges of the blankwhen cold, there will be a tendency toward slightly upsetting the edgesof the seam when heated in the welding operation. This, however, can beregulated by the adjustment of the welding rolls and the spring mountingof the guide roll. The current is kept constant automatically and thevoltage is varied to overcome resistance between the welding rolls. Asthe blank enters the pass between the welding and guide rolls, the rollsare supplied with direct current from the sepa-' rately excitedgenerator, controlled in the manner described above, with the resultthat the pipe at its meeting edges is continuously welded from end toend.

To prevent unequal wear of the contact surfaces of the welding rolls thepolarity of the generator 2 can be changed by means of a reversingswitch 33 in the exciter circuit. The direction of current may thus bereversed for each alternate length of pipe, but. should not a bereversed during the welding of any single length of-pipe.

It will be seen that a workman with ordinary skill can without diihcultyadjust the setting of the relay to the thickness of the material and the.speed of the welding rolls and thereby insure the flow of asubstantially constant direct current across the joint to be welded,which will secure a continuity of welding not attained by any of themethods heretofore in use.

Tubes or pipe may be welded by the method just described at a high speedand such tubes and pipes will be found to be uniformly welded and have asubstantially uniform Wall thickness reac es at the weld, for while insome instances there is a slight burr, this burr is very generally ofuniform character and, in any event, the, welded metal in the region ofthe seam is substantially of the same thickness, uniformity and textureas those portions of the tube wall which are unaffected by the weldingoperation.

The terms and expressions which I have employed are used as terms ofdescription and not of limitation, and I have no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described, or portions thereof, but recognize thatvarious modifications are possible within the scope of the inventionclaimed.

What I claim is:

1. In apparatus for electrically welding a tube blank, a pair of rotarywelding electrodes intended to engage the exterior of the tube andsupply a direct current flow across the seam to be welded; a separatelyexcited generator supplying direct current to said electrodes, andmeans, for changing the polarity of the generator to reverse the currentflow through the electrodes to prevent unequal wear on the surfaces ofthe electrodes.

2. In apparatus for electrically welding a tube blank, a pair of weldingelectrodes for engaging a tube on opposite sides of the seam to bewelded, means for causing the tube to travel longitudinally whileengaged by said electrodes, and a separately excited directcurrentgenerator connected to said electrodes for supplying current thereto,and means for varying the strength of the field of said generator toregulate the voltage supplied thereby.

3. In apparatus for electrically welding a tube blank, a pair of weldingelectrodes, each electrode being mounted upon a rotatable shaft, and

.driving means for each'shaft including a gear meshing with a gear onthe shaft, one of said gears being formed of insulating material.

4. In apparatus for electrically welding a tube blank, a pair of weldingelectrodes for engaging the tube on opposite sides of the seam to bewelded, means for causing the tube to travel longitudinally whileengaged by said electrodes, and means for supplying to said electrodes adirect current of substantially constant value for thereby causing thewalls on the opposite sides of. the seam to be formed into a continuousand uninterrupted weld, said means comprising a separately exciteddirect current generator connected to said electrodes.

5. In apparatus for electrically welding a tube blank, a pair of weldingelectrodes for engaging a tube on opposite sides of the seam to bewelded, means for causing the tube to travel longitudinally whileengaged by said electrodes, and a separately excited direct currentgenerator connected to said electrodes for supplying current thereto,and means controlled by the welding current for varying the strength ofthe field of said generator to regulate the voltage supplied thereby.

WILFRED SYKES.

